Skip to main content

ASP.NET Core–Health checks

ASP.NET Core offers Health Checks Middleware for reporting the health of your application. Health checks are exposed as HTTP endpoints and can be probed by container orchestrators and load balancers to check an app's status.

For Kubernetes I typically create 2 type of health checks:

  • Readiness indicates if the app is running normally but isn't ready to receive requests.
  • Liveness indicates if an app has crashed and must be restarted.

This is a general guideline we use for all containerized applications that we have running in Kubernetes.

Last week I was reviewing one of those applications and I noticed the following code:

This code is perfectly fine, but I couldn’t remember exactly what the role of the Predicate was in the example above. Time to dig in somewhat deeper…

By default, the Health Checks Middleware runs all registered health checks. To run a subset of health checks, you can provide a function that returns a boolean to the Predicate option.

So in the example above, the readiness check will only run healthchecks tagged with ‘ready’. The second health check, the liveness check, will run none of the available health checks.

To tag a specific healthcheck, you should configure this when adding the healthcheck:

More information: https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks?WT.mc_id=DOP-MVP-5001942

Popular posts from this blog

.NET 8–Keyed/Named Services

A feature that a lot of IoC container libraries support but that was missing in the default DI container provided by Microsoft is the support for Keyed or Named Services. This feature allows you to register the same type multiple times using different names, allowing you to resolve a specific instance based on the circumstances. Although there is some controversy if supporting this feature is a good idea or not, it certainly can be handy. To support this feature a new interface IKeyedServiceProvider got introduced in .NET 8 providing 2 new methods on our ServiceProvider instance: object? GetKeyedService(Type serviceType, object? serviceKey); object GetRequiredKeyedService(Type serviceType, object? serviceKey); To use it, we need to register our service using one of the new extension methods: Resolving the service can be done either through the FromKeyedServices attribute: or by injecting the IKeyedServiceProvider interface and calling the GetRequiredKeyedServic...

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...